1. Field of the Invention
The present invention relates to a film formation method and apparatus for a semiconductor process for forming a thin film on a target substrate, such as a semiconductor wafer. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or a glass substrate used for an LCD (Liquid Crystal Display) or FPD (Flat Panel Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
In manufacturing semiconductor devices, various processes, such as CVD (Chemical Vapor Deposition), are performed to form thin films on a target substrate, such as a semiconductor wafer. In film formation processes of this kind, a natural oxide film may be present on a target surface (an under-layer surface), such as the surface of, e.g., a semiconductor wafer or poly-crystalline silicon film. Accordingly, it is necessary to remove the natural oxide film prior to the film formation.
There have been various proposed methods for removing natural oxide films. For example, Jpn. Pat. Appln. KOKAI Publication No. 5-217968 (Patent Document 1) discloses the following processing method. Specifically, a semiconductor wafer is loaded into a reaction chamber, and hydrogen fluoride gas is supplied to remove a natural oxide film. Then, chlorine fluoride gas is supplied while irradiation with ultraviolet rays is used to perform etching. Further, hydrogen gas is supplied while irradiation with ultraviolet rays is used to remove chloride.
However, where the method of Patent Document 1 is used, components of a reaction chamber, such as quartz, may be etched by hydrogen fluoride gas supplied into the reaction chamber. Further, this etching produces water and oxygen, which may generate a natural oxide film and thus make it difficult to obtain a state in which no natural oxide film is present.
In order to remove a natural oxide film while preventing quartz of a reaction chamber from being etched, a method may be adopted of performing wet cleaning of semiconductor wafers outside the reaction chamber. However, where such wet cleaning is used to remove a natural oxide film from semiconductor wafers, another natural oxide film may be formed while the semiconductor wafers are transferred into the reaction chamber. Further, oxygen, moisture, or organic substances may be carried into the reaction chamber at this time and generate a natural oxide film.